A substrate deposition system may be used to process a substrate with an energized gas, such as plasma. Typically, the system includes a deposition chamber which encloses a process zone into which a gas is introduced, a gas energizer to energize the gas, a target which provides a source of material and an exhaust to remove the energized gas. The deposition chamber may, for example, be used to deposit material on the substrate.
The chamber components exposed to the energized gas and sputtered material are often covered with removable shields which protect the surface of the chamber components from the sputtered residues used to deposit material on the substrate. The sputtered material coats the shields during use and unless the shields are removed and replaced, the layer can reach a thickness such that particles begin to flake off and contaminate the process chamber. In subsequent processing cycles, the deposited process residues can flake off of the shield surfaces and fall upon and contaminate the substrate. Therefore, the shields must be frequently and periodically removed and cleaned of surface residue. Manufacturers often use sandblasting to roughen the shield, which allows them to run the sputtering chamber for longer periods of time without a shield change, reducing the down time of process equipment. However, sandblasting leaves particle residue on the surface of the shields which can increase the chances of contamination of the substrate.
U.S. Patent Application Publication No. 2002/0090464 to Jiang et al. relates to a method for preparing a shield for use in physical vapor deposition systems. Initially, a base plate material is shaped to fit inside the physical vapor deposition chamber. The surface of the shield is then degreased with moderate acid etch to prepare for roughening by sand or grit blasting. The grit blasting typically provides an initial surface texture with a roughness value (Ra) up to 250 microinches. The shield is then cleaned and a coating layer between about 0.005 inch to 0.002 inch in thickness is applied by a thermal spraying process, such as thermal arc spraying to produce a surface roughness (Ra) typically in the range of 400 microinches to 1200 microinches. After deposition, the shield is cleaned in an ultrasonic bath and blasted with pressurized air and then baked.
Thus, it is desirable to provide a coated shield which minimizes the amount of flake off of process residue. It is further desirable to provide a coated shield having a high surface roughness and low particle residue to deposit low defect films on substrates and process a larger number of substrates in the chamber while reducing the frequency of chamber downtime for cleaning and replacing of shields.